Genetics lab unravels mystery whale killing at sea

Little was left of the kill when biologists reached the scene.

Observers on a NOAA Fisheries marine mammal survey some 200 miles off the coast of Central California had spotted the telltale signs of a killer whale attack through high-powered binoculars a few miles away. Frenzied swimming churned the ocean surface. Geysers of bloody water sprayed into the air. Hungry seabirds circled in search of leftovers.

But by the time the large research ship arrived at the scene, all biologists could find was a slick of oil from the vanished victim. That, and the unidentified animal's lungs and heart.

Which was all the evidence Brittany Hancock-Hanser needed.

A research biologist in the Marine Mammal Genetics Group at the Southwest Fisheries Science Center in La Jolla, Calif., Hancock-Hanser and her colleagues tease information from the tiniest traces of life. Their target is the DNA that holds every creature's genetic code, defining an animal's species, identity, evolutionary lineage, family relationships and more.

In the case of the recovered lungs and heart, those secrets would provide new insight into the animal the killer whales had attacked.

"We didn't know what that animal was," Hancock-Hanser recalls. "But given the capacity of our lab and how much work we've done on cetaceans, we knew we had a pretty good chance of figuring that out."

Searching the genetic library

The Southwest Fisheries Science Center houses one of the largest collections of tissue and DNA samples from marine mammals and sea turtles in the world, all preserved in giant freezers. It includes about 175,000 tissue samples from roughly 145,000 unique animals and more than 60,000 samples of DNA representing virtually every known species of marine mammal and sea turtle.

Every sample has a unique barcode linked to a database with details about where it came from and how it has been studied.

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Genetics lab unravels mystery whale killing at sea